The sage-steppe ecosystem of western North America is rapidly being converted to an exotic annual grassland (see e.g., Knapp 1996 Association of American Geographers 86:387-411; D'Antonio et al. 1992 Annual Review of Ecology and Sustainability 23: 63-87; Young 1992 Great Basin Naturalist 52:245-252; Chambers et al. 2007 Ecological Monographs: 77: 117-145). With this conversion, populations of hundreds of sagebrush obligate species are decreasing and at risk of extirpation (see e.g., Rowland et al. 2006 Biological Conservation 129: 323-335). Sage-grouse is an obligate species of particular concern that is currently a candidate species for listing under the Endangered Species Act. The listing of sage-grouse has the potential to dramatically limit land use activities in 11 western states, including the entire Great Basin. Annual grass invasion also directly impacts rangeland ecosystem goods and services by decreasing forage production and quality, reducing recreation opportunities, degrading water resources, and increasing fire frequency, which further promotes the dominance and spread of annual grasses (see e.g., D'Antonio et al. 1992 supra; Brooks et al. 2004 BioScience 54:677-688; Davies et al. 2011 Oecologia 167: 481-491; Brunson and Tanaka 2011 Rangeland Ecology and Management 64: 463-470).
Conversion to an exotic annual grassland typically occurs when severe disturbances degrade the system to a point where autogenic recovery is impaired. Large-scale, high intensity wildfires, drought, and over-grazing are common disturbances that can leave sagebrush systems incapable of self-repair (see e.g., Bestelmeyer et al. 2009 Rangeland Ecology and Management 62: 1-15). The resource vacuum that typically occurs following high severity disturbance events increases the susceptibility of the site to weed invasion (see e.g., Miller and Tausch 2001 The role of fire in pinyon and juniper woodlands: a descriptive analysis. Pages 15-30 in K. E. M. Galley and T. P. Wilson (eds.). Proceedings of the Invasive Species Workshop: the Role of Fire in the Control and Spread of Invasive Species. Fire Conference 2000: the First National Congress on Fire Ecology, Prevention, and Management. Miscellaneous Publication No. 11, Tall Timbers Research Station, Tallahassee, Fla.; Bestelmeyer et al. 2009 supra). Land managers can halt the shift to an introduced annual community by successfully reestablishing native or desired non-native species following disturbance (see e.g., Goodrich and Rooks 1999 Control of weeds at a pinyon-juniper site by seeding grasses. In: S. B. Monsen and R. Stevens [EDS.]. Proceedings: ecology and management of pinyon-juniper communities within the interior West. Ogden, Utah, USA: US Department of Agriculture, Forest Service, RMRS-P-9. p. 403-407; Ott et al. 2001 Journal of Range Management 56: 81-91). Unfortunately, the success rate of post-disturbance revegetation efforts is notoriously low (see e.g., Lysne and Pellant 2004 Establishment of aerially seeded big sagebrush following southern Idaho wildfires. Tech. Bull. 2004-01. Boise, Id.: U.S. Department of the Interior, Bureau of Land Management, Idaho State Office. p. 14; Epanchin-Neil et al. 2009 Journal of Environmental Management 91: 370-379; James et al. 2011 Journal of Applied Ecology 48:961-969). Failure rates may approach 90% in many cases, but the true rate of failure is poorly understood, due to the underreporting of negative results in the literature (see e.g., Hardegree et al. 2011 Assessment of range planting as a conservation practice [chapter 4]. In Briske, D. D., ed. Conservation benefits of rangeland practices: assessment, recommendations, and knowledge gaps. US Department of Agriculture, Natural Resources Conservation Service. p. 171-212). Once the site transitions to an annual-dominated system, restoration costs increase dramatically, while the probability of restoring perennial plants back to the system is reduced even further (see e.g., Rafferty and Young 2002 Journal of Range Management 55:70-72; Eiswerth et al. 2009 Journal of Environmental Management 90:1320-1325).
The inability of current restoration technologies to consistently establish native plants from seed indicates that the technologies being used do not address the primary sources of mortality in the progression from seed to established plant (James et al. 2011 supra). This is because much of the effort to restore rangelands with desired perennial species has been based on the scaling-up of decades-old row crop agriculture technology (e.g. re-seeding with seed drills) without taking the time to define specific ecological barriers to restoration success or practices to overcome such barriers. It is now clear that traditional interdictory-based approaches to solving the annual grass problem have not been sufficient to offset losses, despite large monetary investments (see e.g., Kay et al. 1981 Fremontia 9:11-15). Thus, to sustain the ecological integrity and productivity of western US rangelands there is a substantial need to develop methodologies and technologies that result in the establishment of functional plant communities following a catastrophic disturbances.
Fortunately, as will be clear from the following disclosure the present invention provides for these and other needs.